What are the sources of error of a measurement of the length of a board using a steel
tape measure?
There are four main types of errors in a measurement such as this:
The quality of the steel tape measure as manufactured. Certainly some tape measures
are higher quality than others in the accuracy of the measurement marks on the tape, for example.
There are unavoidable conditions, such as the air temperature, that contribute
to the tape's error through thermal expansion and contraction.
The fineness of the measurement marks on the tape puts a limit on how closely
a measurement can be taken.
The person using the tape measure to make the measurement can certainly affect
the error by reading the measurement incorrectly or by being careless in applying the
tape measure to the board.